Mass shootings—particularly in public places—and the associated casualties have increased dramatically in the United States since 2004. Data collected on public mass shootings by Mother Jones magazine reveal a more than 3-fold increase in the number of people shot in these types of shootings between the years in which a federal ban on assault weapons and large-capacity ammunition feeding devices was in place (21.1 per 100 000 citizens per year in 1995 to 2004) and the years since the law expired (65.7 per 100 000 citizens per year in 2005 to 2016) (1). Yet, the direct effect on total firearm-related mortality remains small given that deaths from such shootings account for fewer than 2% of all firearm-related fatalities.

As Studdert and colleagues point out in their article, public mass shootings receive considerable news coverage and elevate public fear and anger (2). Using perhaps the most comprehensive data on handgun purchases available in the United States—a database maintained by the California Department of Justice—along with sophisticated analytic methods for time-series data, the researchers show that the most deadly and highly publicized mass shootings (in Newtown, Connecticut, and San Bernardino, California) were followed by increases in handgun purchases over 6 weeks of 53% and 41%, respectively.

Spikes in sales after high-profile mass shootings have been reported by some news outlets; however, the reporting has relied on convenience samples of retail gun sellers and data from presale background checks tracked by the Federal Bureau of Investigation, both of which can be poor barometers of firearm sales. Furthermore, the potential effect of mass shootings on gun sales is hard to gauge because it is impossible to know from aggregated background check data how many of the checks are for persons who already own 1 or more firearms versus those who may be spurred to buy a gun in response to concerns about mass shootings. Studdert and colleagues' study (3) is the first to answer the question of whether spikes in gun sales after mass shootings principally reflect stockpiling of guns by persons who are already well-armed, or persons choosing to become gun owners. They found that mass shootings have a larger effect on persons becoming handgun owners than on the number of handguns a person owns. Because gun ownership is linked with higher risk for suicide and domestic homicide, mass shootings could indirectly elevate firearm mortality well beyond the deaths that occur in such shootings (3).

The authors offer appropriate cautions about the likelihood that California's response after mass shootings may differ from that in other states because of variations in gun culture and policy across states. It seems likely that gun acquisitions inspired by mass shootings would be greater in most other states that have far fewer regulations governing handgun sales because California has a 10-day waiting period; a safety training requirement; a limit of 1 handgun per person per month; and safety standards that ban the sale of most low-quality and, therefore, low-price handguns. These regulations are lacking in all but a few states. Furthermore, residents of states with more lax gun control laws may be more vulnerable to fears that onerous gun control may follow mass shootings.

The effect of mass shootings on gun violence may be influenced more by the mobilization of political forces to deregulate gun carrying in public places that often follows shootings (4). John Lott has promoted a theory that perpetrators of mass shootings intentionally seek out places where carrying is restricted in order to shoot as many defenseless people as possible. However, this gun-free zone theory of mass shootings does not hold under scrutiny of these shootings, their locations, and the laws in place at the time (5). That citizens who lack rigorous training for responding effectively and responsibly with firearms in crisis situations can thwart mass shootings is also not supported by facts (5, 6).

Lott's research on the purported safety benefits of right-to-carry (RTC) laws has also been debunked (7–9) but has been influential in the enactment of laws repealing prior restrictions and regulations over citizens carrying concealed firearms. During the era of dramatic increases in mass shooting casualties, fears of such shootings have led to more states making public carrying of firearms in virtually all public places legal and normal.

Although earlier research suggested that RTC laws had no effect on violent crime, more recent research that includes more data and more sophisticated analytic methods has consistently found that these laws are associated with more violent crime, especially aggravated assaults. As RTC laws expand and nearly all regulations or restrictions are stripped away, as is the case now for nearly a dozen states that have adopted “permitless” concealed-carry laws, gun carrying becomes more common and the risks to public safety grow. Although those who do get permits to carry concealed firearms are at relatively low risk for committing violent crimes individually, the increase in exposure to firearms in a large and heterogeneous group with respect to risks for violence can lead to more assaults, injuries, and deaths as many people have regular direct contact with loaded firearms.

The best way to counter social and political forces that lead to policies and behaviors that translate into more guns and gun-related violence is not obvious. Careful thought and research need to be devoted to considering what messages, messengers, and vehicles for communication are most effective in environments in which fears of being a victim in a mass shooting are growing and so-called tribal politics are becoming the norm. Telling people that their fears of mass shootings and their urge to defend themselves against such shootings are irrational is unlikely to be effective. Keys to a productive path forward include tracking and publicizing the tragic shootings that occur when persons who legally possess firearms in public places are the shooters, juxtaposing the frequency of these events versus the number of times civilians use guns effectively to thwart attempts at mass shooting, and gaining the trust of gun owners through cultural competence.

Aneja A, Donohue JJ, Zhang A. The Impact of Right to Carry Laws and the NRC Report: The Latest Lessons for the Empirical Evaluation of Law and Policy. Stanford Law and Economics Olin Working Paper No. 461. 4 September 2014. Accessed at https://ssrn.com/abstract=2443681 on 17 April 2017.

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